Solid Hardwood, Engineered and Laminate Flooring - sub floor (over slab)

Here's the deal...I have existing engineered wood floors in part of the house and carpet in the bedrooms. I want to lay a new engineered wood floor (floating) in all of these areas. I understand that the floating floor will lay over top of the existing wood, but I will have to bring the height of the bedrooms up to match it. Which would be better...plywood or luaun? Should I glue it to the slab or ??? What about expansion joints in the sub floor? Thanks.

Might not be the answer you are after but i just did the same thing and i put two layers of under lay on mine and it worked great and matched up almost perfect

Might not be the answer you are after but i just did the same thing and i put two layers of under lay on mine and it worked great and matched up almost perfect

That sounds like a better way to go. Which underlayment did you use?

I used the premier underlay from lowes it has the mosture barrier on one side and the wool looking stuff on the other hope it helps

Never double the underlayment!!!! That will void any warranty the wood manufacturer places on the product. Too much flex with break the glue joint loose, or if it is a click, bust the locking tongue off, both cases the floor begins to separate.